During formal meditation sitting, we often restrict our focus to a single internal image or phenomena, such as the vision of a candle, the sound of our breath, or the sensations in our head. Many claim, with some validity, that this leads to a feeling of tranquility or calm during the process, and afterwards.
While I don’t discount any of this, there is a dangerous side-effect that few meditation teachings acknowledge – that is myopia. Myopia in meditation stems from our focus during the meditation process being so strong that it becomes unsustainable and we eventually react in the opposite direction.
One way to prevent myopia is simply to focus 50% of a cycle. In other words, only 50% of your time during a cycle of meditation should be focus – the rest of the time your mind is free to drift.